Unions in Britain were subject to often severe repression until 1824, but were already widespread in cities such as London. Trade unions were legalised in 1824, when growing numbers of factory workers joined these associations in their efforts to achieve better wages and working conditions. Workplace militancy had also manifested itself as Luddism and had been prominent in struggles such as the 1820 Rising in Scotland, in which 60,000 workers went on a general strike, which was soon crushed. From 1830 on, attempts were made to set up national general unions, most notably Robert Owen's Grand National Consolidated Trades Union in 1834, which attracted a range of socialists from Owenites to revolutionaries. That organisation played a part in the protests after the Tolpuddle Martyrs' case, but soon collapsed.
An important development of the trade union movement in Wales was the Merthyr Rising in May 1831 where coal and steel workers employed by the powerful Crawshay family took to the streets of Merthyr Tydfil, calling for reform, protesting against the lowering of their wages and general unemployment. Gradually the protest spread to nearby industrial towns and villages and by the end of May the whole area was in rebellion, and for the first time in the world the red flag of revolution was flown – which has since been adopted internationally by the trades union movement and socialist groups generally.